This invention relates to a torque yielding wrench used to apply a predetermined torque value to an object work element which may be a bolt, nut, fastener or the like and upon reaching this value will disengage without exceeding this setting.
The importance in industry of a precision wrench which will mechanically limit the amount of turning moment or torque is well known to persons familiar with the general requirements of mechanical fabrication, assembly, service, repair or inspection. Further, there is the requirement for a wrench that, without exceeding this preset value, will upon its attainment disengage the loading system of the wrench from a socket or other connecting member, and upon further rotation will only repeat the cycle of increasing from no-load to predetermined load, and will have the ability to produce this effect through a wide torque range for a series of varying sizes or of loading in subject work fasteners.
Heretofore, mechanical preset spring actuated torque applying wrenches have normally had their actuating springs continuously maintained in a loaded condition throughout their life. This period of existence in a constantly stressed form has had a tendency to shorten the life span by progressive failure and spring crystallization, and require frequent recalibration. Other problems have been their multiplicity of parts and the requirement of high precision in fabrication.
Various inventors have created numerous modifications and variations to achieve a torquing wrench capable of obtaining preset values. U.S. Pat. No. 3,137,187 to Van Hoose (1964) discloses a torque limiting wrench that has a torsion bar and sliding clamp to change the wrench's effective length but is highly complex. U.S. Pat. No. 3,279,286 to Larson (1966) is a preset torque measuring device that uses a split shank of a non-common hand wrench material that must be precisely reproduced, will operate over a limited range and has a working mechanism open to the intrusion of foreign materials such as grease, particles, etc., with the possible modification of the setting or complete failure of the wrench. U.S. Pat. No. 1,512,192 to Benko (1924) is a preset device that uses a lever arm, a pawl member with a sliding mounted spring that applies a varying load to a toothed wheel, and with the difficult ability to consistently reproduce an accurate value. U.S. Pat. Nos. 2,734,412 to Orner (1956), 3,003,378 to Hotchner (1961), 2,427,153 to Mossberg (1947), and 2,674,108 to Latimer (1954) have a similarity of intent but widely varying complex systems.